Flood Potential Outlook
Issued by NWS Binghamton, NY

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Winter/Spring Flood Potential Outlook
National Weather Service Binghamton NY
308 PM EST Thu Feb 16 2017

...WINTER/SPRING FLOOD POTENTIAL OUTLOOK NUMBER 4...

This is the fourth in a series of regularly scheduled hydrologic
outlooks issued during the Winter and Spring season. This outlook
is designed to provide a generalized assessment of river flood
potential (not flash flooding) across Central New York and
Northeast Pennsylvania for the next two weeks...February 16th to
March 2nd.

...SUMMARY...

The flood risk with respect to existing hydrologic conditions
varies across the major river basins. Conditions suggest a
seasonally average risk of flooding in the North Branch
Susquehanna and Upper Delaware basins, while the Chemung and Upper
Mainstem Susquehanna are generally below the seasonal average. The
Finger Lakes basins are also split between below average risk in
the western half, to near normal flood potential in the eastern
half.

...CURRENT CONDITIONS...

.PRECIPITATION: Above Normal. For the past two weeks,
precipitation was more than 150 percent of normal across Central
New York and near 100 percent of normal in Northeast Pennsylvania.
Overall, 1 to 3 inches of precipitation fell around the region
with locally higher amounts in the higher terrain of the
Susquehanna and Upper Delaware basins. Heavy lake effect snow has
brought as much as 4 to 5 inches of liquid equivalent to the Tug
Hill plateau.

.SNOW COVER AND WATER EQUIVALENT: Variable. Snow cover was near
to above normal in the North Branch Susquehanna, Delaware and
Eastern Finger Lakes basins, but below normal across the Chemung,
Western Finger Lakes and Upper mainstem Susquehanna in Northeast
Pennsylvania. Snow depths ranged from 6 to 12 inches in the east,
with spotty amounts approaching 2 feet at higher elevation, to
generally under 3 inches in the western half of the area. Water
equivalent in the deeper snowpack averaged 2 to 4 inches, with
less than an inch in snow sparse regions.

.RIVER ICE COVER: Much Below Normal. As of February 15, most
river channels were more than 80 percent open with just some thin
border ice along the river banks.

.STREAMFLOW AND SOIL CONDITIONS: Normal to Above Normal.
Streamflow, averaged over the last 14 days, ranged from above
normal flows in New York, to near normal flows across the
northeast Pennsylvania rivers. Soils were wetter than average
throughout the region. Soil temperatures in the 2cm to 10cm layer
remained in the low to mid 30s, however, there have been scattered
reports of a thin frost layer down to 2 feet in some areas.

.RESERVOIR AND LAKE LEVELS...Variable. The Finger Lakes were at near,
to slightly above normal winter pools. The NYC Delaware reservoir
system was below normal, however, recharging had made significant
gains in the last few weeks. Lake Wallenpaupack was near normal.

...FORECAST OUTLOOK...

.FUTURE WEATHER CONDITIONS: The 6 to 14 day outlook calls for
significantly warmer than normal temperatures and above normal
precipitation. The first week within this outlook period will
become milder than normal at a gradual pace, and remain generally
drier than average. Heading into week two, mild temperatures continue,
but the storm track appears to become more active with a chance for
better than average rainfall by the end of the outlook. No major storm
systems are on the horizon at this time.

.LONG RANGE RIVER MODELING AND PROBABILITY FORECASTS: A blend of river
forecast models suggests a 10 percent or less chance of flooding during
the next two weeks at most locations. There is a 30 percent chance
or less probability that some of the headwater gauges on the Susquehanna
and Delaware tributaries could approach flood stage if a rain event
developed during the second week.

A climatological analysis of flooding, using current hydrologic conditions
compared to historical flows, suggests the chance of significant river
flooding during the two week period is near normal for the Susquehanna
and Delaware basins, but generally below normal for the Chemung and
Finger Lakes basins.

...IN CONCLUSION...
This outlook estimates the potential for river and lake flooding
based on a current overview of hydro-meteorological factors which
contribute to flooding.

It is important to note that significant flooding does not occur
from snow melt alone. Rainfall, how much and in how short a period
of time, is the most important factor in determining the severity
of flooding. Specific forecasts of heavy rainfall and flash
flooding are not included in this outlook.

The next Winter/Spring Flood Outlook will be issued by this
office in two weeks, on March 2, 2017. If conditions change in the
interim: Flood Watches, Warnings or Advisories will be issued as
necessary.

$$

JAB



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